1. Field of Invention
The present invention relates generally to cancer detection and, more particularly, to cancer detection involving the measurement of nitric oxide associated with cancerous tissue. The present invention directly detects nitric oxide in tissue and, therefore, by its presence serves as an indicator of cancerous cells. While nitric oxide dependent cancer detection is applicable throughout the human body, it is particularly applicable to the human breasts. Nitric oxide concentration is determined by drawing a sample of interstitial fluid from a breast, preferably through a small gauge needle, and analyzing the fluid using conventional techniques.
Before the present invention, a full work-up, generally comprising an ultrasonic scan, needle or incision biopsy, or stereotactic biopsy is preceded by a positive finding on a breast cancer screening test, such as a positive mammographic image, and followed by a histopathological study. The present invention is not necessarily a screening test but is used as a confirmation of a positive result from a screening test. If the results of the present test are confirmatory, i.e., nitric oxide is present in the breast tissue, a biopsy is performed as a double check. If, on the other hand, it is determined that nitric oxide is not present in the breast and, consequently, that the screening test was erroneous, the patient is spared the trauma of having to undergo the full work-up including the biopsy. In that respect, confirmation of cancerous lesions by measuring nitric oxide concentrations in tissue has many significant differences and advantages over conventional breast cancer tests, as well as cancer detection methods in general.
2. Prior Art
Up to now, cancerous lesions have been generally located by their space occupying properties detectable by palpation or by imaging techniques, such as X-ray mammography (XRM), X-ray computerized tomography (CT), ultrasonic imaging, or magnetic resonance imaging (MRI). In certain cases, such as in a human breast, detection of cancer is also made possible by the enhanced blood supply (hyperperfusion) associated with the neoplastic lesion. A technique which takes advantage of this hyperperfusion is Dynamic Area Telethermometry (DAT), which is fully described in the Applicant's patent application Ser. No. 08/368,161 filed Jan. 3, 1995. That application is licensed to the assignee of the present invention and incorporated herein by reference.
The various prior art cancer detection methods are based on secondary indicators resulting from the growth of the cancerous lesions. For example, XRM uses the higher density of calcium minerals and the higher absorbance of X-rays in calcium atoms, due to the photoelectric effect, to detect microcrystals of calcium minerals, generally calcium phosphates, that deposit interstitially in cancerous tissue. The characteristic shadow of the relatively opaque microcrystals of calcium minerals on the radiograms indicates their presence in tissue. Since pathological microcalcification occurs subsequent to tumor formation, it occurs later than the proliferation of cancerous cells producing nitric oxide, and the immune response to neoplastic cells, which invokes macrophage activity that also produces nitric oxide. Therefore, nitric oxide is present in a cancerous breast before detection is possible by XRM. Also, one of the major draw-backs of XRM as a breast cancer screening test is the occurrence of microcalcification or calcification in benign lesions. Hence, only a fraction of breasts that manifest microcalcification contain malignant tissue. False positive XRM results are common, and lead to full diagnostic work-ups which often prove to be negative for breast cancer.
In order to prevent full diagnostic work-ups predicated on false positive XRM results, there is needed a confirmation test that is easy to administer, inflicts a minimal amount of trauma to the patient and gives accurate results on which a physician can confidently subject the patient to a surgical procedure to remove the lesion, if present. Since the outcome of treatment of cancer, and particularly breast cancer, is more favorable the earlier and more accurately the cancer is detected, the present invention is a substantial advancement in improving public health by conclusively indicating the presence of cancerous lesions.